vehicle vs wall

let's say you drive a 4 wheel rc car towards a wall. what's the force required to drive the front wheels up the wall?

i've been told that each tire needs to produce LESS than 1/4 the total weight of the car. i just can't work it out that way.

this is a design project problem. they don't make motors torquey enough to produce 1/4 the weight of my little car, but it's close. if it's slightly less, i'm saved and i can find some motors. see if you guys can work this out better than i can. save my life.

As a bonus, why not put something on the front of the car that will hit the corner between the wall and the floor and push up/backwards (a little). That would reduce the whole risk of just hitting the wall and bouncing back.

Does anyone think that's not totally retarded? I think it might help.